The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, a CVVT (Continuous Variable Valve Timing) is applied to a vehicle to reduce an exhaust gas and improve fuel efficiency and output. Recently, intermediate phase CVVT systems for removing limits in response and operation period of existing CVVT systems have been developed and those intermediate phase CVVTs control the position of a cam, not at the most advanced (intake) position and the most delayed (exhaust) position, but an intermediate position, so response is quick and the use period of a cam can be increased, so fuel efficiency is improved and an exhaust gas is reduced.
In intermediate phase CVVTs, a lock pin on the rotor is locked into a lock pin hole between an advancing chamber and a retarding chamber while the RPM of an engine is reduced, thereby preparing for later engine start. The action that the lock pin is automatically locked into the lock pin hole while the RPM of an engine reduces is called ‘self-lock’.
The self-lock is a function that allows a CVVT system to mechanically return to an accurate position without specific adjustment so that operational stability of an engine can be maintained in periods where the CVVT system is not used, that is, when the engine is idling or is started.
However, when the valve timing reaches the most delayed position without returning to the intermediate phase, and an engine of a vehicle is idling, a surge tank may not be vacuumized and the internal pressure of the surge tank may increase up to the atmospheric pressure, so the performance of a brake using the vacuum of the surge tank may be deteriorated.
Further, when the valve timing reaches the most delayed position without returning to the intermediate phase, excessive overlap of valve timing may be generated between an intake valve and an exhaust valve, so the operational stability of the engine decreases and vibration of the engine increases, and in some cases, the engine stops.
That is, with a rotor and a lock pin positioned at the most advanced position or the most retarded position, when self-lock of a lock pin in an intermediate phase CVVT may not be automatically performed, negative pressure is not generated, so an engine is stopped or a brake system may not operate.
Accordingly, as shown in FIG. 3, a diverter valve 10 controlling a channel 30 is provided for self-lock of an intermediate phase CVVT 50 to open or close the channel 30, so a channel for supplying oil for operating the CVVT 50 is formed or hydraulic balance in an advancing chamber or a retarding chamber is maintained.
However, we have discovered that when the diverter valve is operated, side force is generated by oil pressure, so the diverter valve may not operate normally.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the foregoing is already known to those skilled in the art.